Grass mowing machines may include material collection system sensors that are intended to sense if the collection container is full. For example, some material collection systems include sensors that detect air pressure in the discharge chute as shown in U.S. Pat. Nos. 5,388,394, 5,605,033, 5,775,077, 5,950,408, 6,073,432 and 6,622,465. These sensors are not easily adjustable to compensate for differences in material flow of wet grass clippings and dry grass clippings through the discharge chute into the collection container.
Other material collection system sensors include pivotable devices that contact grass clippings in the container as shown in U.S. Pat. Nos. 4,969,320 and 6,272,818; electrical conductivity sensors as shown in U.S. Pat. Nos. 4,964,266 and 5,960,613 and European Patent Application EP2020173A1; sensors that detect resistance to oscillation as shown in U.S. Pat. No. 5,832,708; light sensors as shown in U.S. Pat. No. 5,321,939; and weight sensors as shown in U.S. Pat. No. 4,981,011. These sensors also are not repeatable for wet grass clippings and dry grass clippings, or difficult to adjust for sensitivity to moisture and weight of collected material.
There is a need for a material collection system sensor that can be easily adjusted for moisture and weight of wet grass clippings and dry grass clippings. There is a need for a material collection system sensor that can help maximize the amount of material collected in the container, without the discharge chute becoming plugged with grass clippings. There is a need for a material collection system sensor that can be used on a rear discharge rear collection mower.